1. Field of the Invention
The present invention relates generally to turret punch presses having a pair of upper and lower turrets on which a plurality of pairs of upper and lower punching tools can be mounted to punch a variety of holes in sheet materials such as sheet metals. More particularly, the present invention rlates to apparatus for synchronously indexing or rotating the upper and lower punching tools in the upper and lower punching turrets in the turret punch presses to make the best use of the punching tools.
2. Description of the Prior Art
As is well known, the turret punch press comprises a vertically movable ram and a pair of rotatable upper and lower turrets for holding a plurality of upper and lower tools which are varied in size and shape to punch a variety of holes in sheet materials such as sheet metals. The upper and lower turrets are vertically spaced from each other substantially beneath the ram and horizontally disposed on their respective shafts which are vertically disposed so as to coaxially align with each other. Each of the upper punching tools on the upper turret is so located as to vertically align with either of the lower tools on the lower turret in order to cooperate with each other to punch holes of a peculiar shape. Also, the upper and lower turrets are so arranged as to be simultaneously rotated by power to bring a desired pair of the upper and lower tools into a position just beneath the ram so as to enable them to be worked by the ram to punch holes of a desired shape. In this arrangement, a workpiece such as a sheet metal to be punched is horizontally fed by a plurality (usually a pair) of clamping means into a position between the upper and lower turrets namely the upper and lower tools which have been placed just beneath the ram by the upper and lower turrets. The clamping means are so arranged as to grip an end of the workpiece and be moved by power along both the X and Y axes namely in all directions toward and away from the upper and lower turrets to bring any portion of the workpiece into a position beneath the ram. Also, in order to automatically and continuously punch a number of holes varied in size and shape in the workpiece, the upper and lower turrets and the clamping means are so arranged as to be rotated and moved under a numerical control which is preprogrammed.
In punching operations in the turret punch presses of the above described arrangement, it is very often desired to punch a plurality of holes which are all the same in shape and size but are different in direction in worksheets. For example, there are cases where it is desired to punch in a workpiece many holes of T-shape and inverted T-shape which are quite identical in shape and size and are different only in direction. As another example, it is often necessary to punch in a workpiece many I-shaped holes identical in shape and size at different angles to an edge of the workpiece. Of course, there are cases where it is desired to punch holes identical in shape and size in a direction in some workpieces and in different directions in other workpieces.
In the conventional turret punch presses, however, it has been impossible to satisfactorily punch holes identical in shape and size in different directions in workpieces in an economical manner. For instance, in order to punch holes in diffeent directions in workpieces, a desired pair of the upper and lower tools of a desired shape and size are manually adjusted in direction in the upper and lower turrets in a conventional turret punch press. As a matter of course, however, it is very difficult and time-consuming to accurately align the upper and lower tools in a desired direction in the upper and lower turrets in this manner. Therefore, for the purpose of easy alignment, each of the upper and lower tools is provided with an alignment key and each of the upper and lower turrets is formed with a plurality of grooves with which the alignment key is to be selectively engaged in some of conventional turret punch presses. In this manner, however, of course it is impossible to smoothly adjust the upper and lower tools in any direction in the upper and lower turrets to punch holes common in shape and size in all directions in workpieces. Also, it is still time-consuming and troublesome to manually change the upper and lower tools in any direction in the upper and lower turrets, and furthermore the arrangement is costly since it is necessary to form a plurality of grooves in the upper and lower turrets. Anyway, as a greatest disadvantage, it is impossible to continuously punch holes which are identical in shape and size and different in direction without discontinuing the punching operation in the arrangements in which the upper and lower tools are to be manually changed in direction in the upper and lower turrets. In order to punch holes different in direction in workpieces in this manner, it is necessary to discontinue the punching operation to change the upper and lower tools in direction after having punched holes common in direction.
For the above described reasons, it has been often the case that many pairs of upper and lower tools which are all the same in shape and size are mounted together on the upper and lower turrets to continuously punch a variety of holes including those which are common in shape and size and different only in direction. In this case, however, of course the high cost is inevitably necessary for the upper and lower tools and also the trouble is that only a limited number of pairs of the upper and lower tools can be mounted on the upper and lower turrets.